Mobile wireless communication devices, such as a cellular telephone or a wireless personal digital assistant, can provide a wide variety of communication services including, for example, voice communication, text messaging, internet browsing, and electronic mail. Mobile wireless communication devices can operate in a wireless communication network of overlapping “cells”, each cell providing a geographic area of wireless signal coverage that extends from a radio network subsystem. The radio network subsystem provides an “air interface” through which the mobile wireless communication device can access the wireless communication network. Whether idle or actively connected, a mobile wireless communication device can be associated with a “serving” cell in a wireless communication network and be aware of neighbor cells to which the mobile wireless communication device can also associate. The quality of a communication link between the mobile wireless communication device and the radio network subsystem can vary based on the distance between them and on interference included in received signals at either end of the air interface. As the mobile wireless communication device moves further away from the radio network subsystem, eventually a neighbor cell can provide an equal or better performing communication link than the current serving cell. The mobile wireless communication device can include a process for determining if and when to switch cells with which it associates. If the mobile wireless communication device is actively connected to the serving cell, then the process of switching to a neighbor cell is known as “handoff.” For a mobile wireless communication device that is associated with a serving cell in an “idle” state, the process of associating with a neighbor cell is known as “cell reselection.”
When a mobile wireless communication device seeks to associate with a wireless communication network, such as after a power on initialization, the mobile wireless communication device can search for cells located in its vicinity. Initially locating and connecting to a serving cell by a mobile wireless communication device can be referred to as “cell selection”. If a cell is located that is deemed suitable to provide a wireless communication link, e.g. signals from the cell exceeds certain performance quality metrics, then the mobile wireless communication device can associate with that cell. The mobile wireless communication device can be referred to as being “camped” on a particular “serving” cell in the wireless communication network of cells. While camped on the serving cell, the mobile wireless communication device can listen to messages broadcast from the serving cell's radio network subsystem as well as from other radio network subsystems located in neighbor cells. System information that specifies certain properties of the serving cell and its neighbor cells can be broadcast regularly by the serving cell's radio network subsystem. If the mobile wireless communication device determines that a neighbor cell can provide a higher quality communication link than a current serving cell, then the mobile wireless communication device can disassociate from the current serving cell and associate with the neighbor cell, in a process known as “cell reselection”.
The length of time that a battery can power the mobile wireless communication device can differentiate the mobile wireless communication device from other products in today's competitive marketplace. Reducing power consumption in the mobile wireless communication device, e.g. by disabling certain components when they are not required, can extend battery life significantly. When the mobile wireless communication device is connected to the serving cell in an “idle” mode, the mobile wireless communication device can “wake” to read certain system information messages broadcast by the serving cell's radio network subsystem and “sleep” in between readings to conserve power. Some of the system information messages broadcast by the radio network subsystem can be broken into a series of individual segments, with each segment being transmitted separately. The mobile wireless communication device can “wake” to read a segment and “sleep” between segments.
As the connection between the mobile wireless communication device and the serving cell's radio network subsystem can vary in signal strength and interference levels over time, some of the transmitted segments of the system information message can be received correctly while other segments can include transmission errors. The mobile wireless communication can be unable to decode a reassembled system information message that includes segments received with errors. The system information message can be re-broadcast by the radio network subsystem at regular intervals, so the mobile wireless communication device can read the system information message again. Rereading all of the segments of the broadcast system information message to reassemble it correctly, however, can increase “wake” time and thereby reduce battery power. The mobile wireless communication device can unnecessarily “wake” to read segments of the system information message previously received correctly. Selective reading of only certain segments of the system information message can increase “sleep” time and thereby conserve reduce power consumption and preserve battery power instead.